This invention relates to receiving and rotating strips of material and placing the rotated strips in surface contact with a continuously moving web.
1. Field of the Invention
The present invention relates to apparatus and to a method for handling materials in web form by cutting pieces from a slowly-moving first web and placing the cut pieces in predetermined spaced relationship on a faster-moving second web. More particularly, the present invention relates to apparatus and to a method for continuously cutting pieces from a first web, feeding the cut pieces, and associating the cut pieces of material with a second, carrier web that travels at a higher speed than that of the first web, and without stretching either the first web or the cut pieces.
2. Description of the Related Art
A number of different types of apparatus and methods have been devised to permit the feeding of sheets or pieces of material in predetermined spaced relationship along a moving carrier web. Generally, the carrier web is traveling at a higher speed than is the web of material from which the sheets or pieces are cut that are to be associated with the moving carrier web. When the respective webs of the materials to be joined are traveling at different speeds, such as is the case when cut pieces are to be deposited on a carrier web in spaced relationship relative to the direction of movement of the carrier web, the cut pieces move at a rectilinear speed that is slower than that of the carrier web so that the cut pieces can be properly spaced from each other when they are deposited on the carrier web. The cut pieces are then accelerated to match the rectilinear speed of the carrier web for placement thereon in a desired position. However, when the material from which the pieces are to be cut is extensible when placed under relatively low tension, the control of the length of the cut piece and its proper positioning on the carrier web is rendered more difficult because of the likelihood of stretching of the material during the steps of feeding, cutting, and transferring the cut pieces.
One technique that has been devised for matching the speeds of webs or sheets to be joined that initially are traveling at different speeds is disclosed in U.S. Pat. No. 5,693,165, entitled xe2x80x9cMethod and Apparatus for Manufacturing an Absorbent Article,xe2x80x9d which issued on Dec. 2, 1997, to Christoff Schmitz. That patent discloses a laterally-moving shuttle that oscillates back and forth to periodically increase and decrease the speed of one of the parts to be joined, so that its speed can be matched with that of a carrier web in order to properly register cut pieces on the carrier web. However, the oscillatory movement of the shuttle imposes undesirable fluctuating stresses on the apparatus.
Another arrangement for joining parts of webs that travel at different speeds is disclosed in U.S. Pat. No. 5,759,340, entitled xe2x80x9cApparatus For Applying Discrete Parts Onto A Moving Webxe2x80x9d, which issued on Jun. 2, 1998, to Boothe et al. That patent shows an arrangement in which an vacuum roll has radially shiftable segments that rotate about a common axis to allow changes in the speed of pieces cut from one web so they can be transferred to a second, faster-moving web.
A further approach to transferring and joining cut pieces to a moving web wherein the pieces and the moving web are traveling at different speeds is disclosed in U.S. Pat. No. 6,022,443, entitled xe2x80x9cMethod And Apparatus For Placing Discrete Parts Onto A Moving Webxe2x80x9d, which issued on Feb. 8, 2000, to Rajala et al. That patent discloses the use of non-circular drive gears for driving a transfer mechanism that transfers the cut pieces, wherein the speed of the cut pieces can be changed to allow them to be properly registered with and positioned on the moving web.
Although the prior art contains disclosures directed to apparatus and methods for joining together two moving components that are initially moving at different speeds, the arrangements disclosed above can impose significant tension on the slower-moving element. Accordingly, if the slower-moving element has a low modulus of elasticity, significant stretching of the material can occur, which can be an undesirable condition if specific dimensional relationships must be maintained between the size of that element and its position relative to the component to which it is desired to be joined.
It is an object of the present invention to overcome the deficiencies of the prior art apparatus and methods.
Briefly stated, in accordance with one aspect of the present invention, a rotatable vacuum roll is provided for receiving a moving web, for guiding the web, and for transferring pieces cut from the web in timed relationship with a moving carrier web that passes over a portion of the periphery of the roll. The vacuum roll includes a cylindrical shell having a plurality of substantially longitudinally-extending rows of apertures that extend therethrough. A pair of axially-spaced end walls are secured to the shell and define shell ends. One end wall is an apertured end wall that includes a plurality of ports that extend through the apertured end wall and that are in fluid communication with respective rows of apertures in the shell. A stationary vacuum manifold is in surface contact with the apertured end wall, and it has at least one arc-shaped slot facing the apertured end wall for applying vacuum to selected rows of shell apertures through respective end wall ports as the roll rotates relative to the manifold.
In accordance with another aspect of the present invention, a method is provided for feeding, cutting, and transferring pieces of material from a moving web that is traveling at a slower rectilinear speed than the surface speed of the rotating vacuum roll to minimize elastic deformation of the web material.